Application Digest 24445

Measuring gear transmission variations

Richard J. Will, Chief Engineer, Delroyd Worm Gear

When engineers want to reduce the output shaft speed of a motor or engine, while increasing torque, they typically turn to a gear drive. Gears are never perfect, and minor variations in the manufacture of the gears used in drives result in transmission variations.

These variations cause slight changes in the drive's output rpm each time a gear tooth goes into or out of mesh. If an application requires very accurate drive output speed, these errors can become a significant problem. Delroyd Worm Gear Division of IMO Industries can measure and analyze the shaft speed variations caused by gear imperfections.

Delroyd's CSF/2 Single Flank Gear Tester consists of portable input and output encoders, a signal processor and a recorder. The user mounts encoders on the input and output shafts of assembled reducers. Inspection data record the angular variations of the output shaft relative to the input shaft while the gears rotate.

Data obtained by using such test equipment can determine the suitability of a specific drive for an application. It can also enable companies to perform quality control on vendors' products, and alert suppliers to problems before they become lethal.

To speak with a Delroyd applications engineer, call: (609) 890-6800.

Applying capacitive accelerometers

John M. Kubler Vice President, Kistler Instrument Corp.

Recent advances in silicon micromachining technology have made a new variety of acceleration sensors available for measuring low-level, low-frequency vibrations, as well as slowly moving phenomena. In fact, these sensors provide accurate output even when the motion temporarily halts--and they maintain that reference indefinitely.

Performance of variable capacitance accelerometers closely matches that of larger, heavier, and more expensive servo accelerometers. Weighing just 3 to 10 grams, many of these units mount on printed circuit boards for easy system integration. These units can be designed for analog or bit-stream digital output.

When compared to piezoresistive microsensors, capacitive accelerometers offer greater sensitivity. This allows a high signal-to-noise ratio over a wide dynamicrange(>100dB at 100 Hz bandwidth).

Capacitive accelerometers also operate over a wider temperature range (-55 degrees C to +125 degrees C). Such advantages allow low-frequency measurement with very little drift. Variable capacitance accelerometers, therefore, may be of interest to original equipment manufacturers of guidance and control systems, vibration control instruments, and stabilization systems.

To speak with an applications engineer from Kistler Instrument Corp., call 716-691-5100, or fax 716-691-5226.